London, ON – Franklin
D. Roosevelt famously warned that the only thing we have to fear is fear itself.
New research from The University of Western Ontario reveals that FDR’s
rhetorical flourish also accurately reflects a fundamental truth within the
animal kingdom too.

In
a study published today in Science,
findings from a team led by Western biology professor Liana Zanette prove
perception – in this case, fear – of predation risk is powerful enough to
affect wildlife populations even when predators are prevented from directly
killing any prey.

The
traditional view of predators is that they kill prey, and that direct killing
is the only way predators can affect prey numbers. But predators also scare
prey and wildlife live with this fear of being torn limb from limb by some
predator every moment of every single day of their entire lives,” explains Zanette,
a principal investigator at Western’s Advanced Facility for Avian Research. “This
state of fear can be as important as direct killing in reducing prey numbers.

The
ground-breaking research was conducted on song sparrows nesting in British Columbia’s
southern Gulf Islands. The researchers first protected every song sparrow nest
from predators by surrounding them with netting and electric fences. The
researchers then played different sounds to different groups of birds
throughout the four-month breeding season. One group heard sounds associated
with their natural predators while the others heard non-threatening natural
sounds.

Zanette
and the team discovered that the birds that heard the predator sounds produced
40 per cent fewer offspring. Such large reductions in numbers due simply to the
sound of fear, unambiguously show for the first time in any wild bird or mammal
that predators do significantly affect the population sizes of their prey not
just by killing prey, but by scaring them as well.

“This
has important implications for conservation and wildlife management because it
suggests that the total impact of predators on prey populations will be
underestimated if the effect of fear itself is not considered,” says Zanette.
“This means that the adverse effects of introduced predators are likely worse
than previously imagined and the disturbance to native ecosystems due to the
loss of native predators has probably been greater than we previously thought.”

FDR on Fear

"This great Nation will endure as it has endured, will revive and
will prosper. So, first of all, let me assert my firm belief that the
only thing we have to fear is fear itself -- nameless, unreasoning,
unjustified terror which paralyzes needed efforts to convert retreat
into advance."